Mars
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System after Mercury. In English, Mars carries a name of the Roman god of war, and is often referred to as the "Red Planet" because the reddish iron oxide prevalent on its surface gives it a reddish appearance that is distinctive among the astronomical bodies visible to the naked eye. Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the valleys, deserts, and polar ice caps of Earth. Geology We know a lot about Mars from data collected by telescopes and spacecraft as well as by examining meteorites that have come from Mars. Most of the meteorites from Mars are igneous rocks known as basalt. The oldest Mars meteorite is ALH84001, which is 4.1 billion years old. It is a rock type known as an orthopyroxenite. It also has minerals that formed by reactions between the original material and water that formed 3.9 billion years ago. The oldest known minerals from Mars are 4.4 billion-year-old zircons from a 2.1 billion-year-old meteorite (NWA 7034) found in Northwest and its pairings, which are analogous to the ancient Jack Hills zircons on Earth. The youngest known rocks from Mars are basaltic meteorites, rocks known as shergottites, the youngest of which are about 180 million years old. Rocks and Minerals On Mars and in meteorites from Mars, we see a variety of rock types: igneous basalt, sedimentary sandstone, mudstone, impactites, evaporites. These rocks are composed of minerals such as olivine, pyroxene, amphiboles, feldspar, carbonates, sulfates (jarosite, gypsum), silica, phyllosilicates, phosphates, and iron oxides (hematite). Surface Features We also see a variety of familiar landforms, like wind-formed dunes. Other kinds of sedimentary deposits are present as well, known by names such as Transverse Aeolian Ridges (or TARs) and Polar Layered Deposits (PLDs). One of the more intriguing features found on Mars is known as Recurring Slope Lineae (RSL). These features appear and fade in gullies and crater walls as the seasons and temperatures change on Mars. One theory suggests the dark streaks may be made by very salty, liquid water seeping to the surface and quickly evaporating. Some familiar places on Earth are often used by scientists as analogs for the kinds of environments that exist on Mars. Examples include Iceland (the basalt rocks in Iceland contain more iron, like the basalts on Mars do, and Iceland has volcanoes that erupt into glaciers), Antarctica (which, like Mars is very cold and dry), the Atacama Desert in Chile (where it is very dry with similar rocks), Arizona (which has basaltic volcanism on eroded, stratified rock sequences), and Hawaii (made up of large basaltic shield volcanoes like Olympus Mons on Mars). Mars and Earth Geologically, Mars and Earth share a lot of common traits, and they are both known as terrestrial (or rocky) planets. The majority of the rocks at the surface of both planets are of the igneous variety, known as basalt (although on Earth most of this makes up the ocean floor). The layers that make up both planets are also similar: Like Earth, Mars has an atmosphere, crust, mantle, and a core. The rocky layers are similar in composition. In fact, all of the rocks and all of the minerals identified on Mars to date are also found on Earth. Like Earth, Mars has four seasons and weather. Mars has two moons, Phobos and Deimos. Of course, there are a lot of ways that the two planets are different too. Mars is smaller, has no active plate tectonics and no currently active global magnetic field. Liquid water is generally not stable on Mars, so there currently are no standing bodies of water (rivers, lakes or seas) and the atmosphere is very thin and composed mostly of carbon dioxide. Mars has more craters still scarring its surface than Earth (where, because of plate tectonics and weathering, lots of the surface is changed over time). Atmosphere Mars’ atmosphere is composed primarily of carbon dioxide (about 96 percent), with minor amounts of other gases such as argon and nitrogen. The atmosphere is very thin, however, and the atmospheric pressure at the surface of Mars is only about 0.6 percent of Earth’s (101,000 pascals). Scientists think that Mars may have had a thicker atmosphere early in its history, and data from NASA spacecraft (the MAVEN mission) indicate that Mars has lost significant amounts of its atmosphere through time. The primary culprit for Mars’ atmospheric loss is the solar wind! Astrobiology Astrobiology is a relatively new field of study, where scientists from a variety of disciplines (astronomy, biology, geology, physics, etc.) work together to understand the potential for life to exist beyond Earth. However, the exploration of Mars has been intertwined with NASA’s search for life from the beginning. The twin Viking landers of 1976 were NASA’s first life detection mission, and although the results from the experiments failed to detect life in the Martian regolith, and resulted in a long period with fewer Mars missions, it was not the end of the fascination that the Astrobiology science community had for the red planet. The field of Astrobiology saw a resurgence due to the controversy surrounding the possible fossil life in the ALH84001 meteorite, and from the outsized public response to this announcement, and subsequent interest from Congress and the White House, NASA’s Astrobiology Program and one of its major programs, the NASA Astrobiology Institute were formed. Also at this time, NASA’s Mars Exploration Program began to investigate Mars with an increasing focus on missions to the Red Planet. The Pathfinder mission and Mars Exploration Rovers (Spirit and Opportunity) were sent to Mars to “Follow the Water,” recognizing that liquid water is necessary for life to exist on Earth. After establishing that Mars once had significant amount of water on its surface, the Mars Science Laboratory (which includes the Curiosity rover) was sent to Mars to determine whether Mars had the right ingredients in the rocks to host life, signaling a shift to the next theme of “Explore Habitability”. MEP is now developing the Mars 2020 rover mission to determine whether life may have left telltale signatures in the rocks on Mars’s surface, a further shift to the current science theme “Seek the Signs of Life”. Finding fossils preserved from early Mars might tell us that life once flourished on this planet. We can search for evidence of cells preserved in rocks, or at a much smaller scale: compounds called biosignatures are molecular fossils, specific compounds that give some indication of the organisms that created them. However, over hundreds of millions of years these molecular fossils on Mars are subject to being destroyed or transformed to the point where they may no longer be recognized as biosignatures. Future missions must either find surface regions where erosion from wind-blown sand has recently exposed very ancient material, or alternately samples must be obtained from a shielded region beneath the surface. This latter approach is being taken by the ExoMars rover under development where drilled samples taken from a depth of up to 2 meters will be analyzed. Timeline Past Mars provides an ideal landscape for understanding the early history of the solar system and how small planets transform over time. The terrestrial planets Venus, Earth, and Mars formed over 4.5 billion years ago from similar building blocks of minerals and elements. Nevertheless, their transformation over time to the present has followed dramatically different paths. Venus presently has a thick atmosphere made primarily of carbon dioxide with surface temperatures and pressures ~450 C and 92 atmospheres. Although Venus may once have had an ocean its present surface is dry. Mars, on the other hand, has surface pressures that are only around 1 % of the surface pressure at Earth and surface temperatures that seldom reach the melting point of ice and plunge dramatically at nighttime even in mid-latitude regions. Early on, we now know that Mars had rivers and large lakes and perhaps even a northern ocean. The history of Mars since this point is one of dehydradation, gradual loss of a significant portion of its atmosphere, and near surface water turning into ice. Were the early wet conditions favorable for the emergence of life and how long could this life persisted if it did form? Microbial life on Earth that emerged early in its geological history occupies nearly every available niche that provides sufficient energy in the form of transportable nutrients and even Earth’s atmosphere currently bears the stamp of life with most of the oxygen present in the atmosphere produced over time by microbes. Likewise, methane in the atmosphere that can be destroyed by photochemistry over periods of several hundred years is constantly replenished by a variety of biological sources. We have not yet found evidence of past or present life on either Venus or Mars or on any extraterrestrial body for that matter, although this fundamental question motivates our missions of exploration and programs such as the MEP. Present Despite the fact that Mars may once have been warm and wet, it is now a cold, dry, barren place. The atmosphere is thin and mainly carbon dioxide. Ultraviolet and other forms of intense radiation bathe the surface, because Mars has a thin atmosphere and no active magnetic field to protect it. The primary geological processes currently shaping its surface are impact cratering, wind-driven transport of sediment, condensation/sublimation of water and carbon dioxide ice, and landslides. However, there are many things we do not yet know about Mars, or do not know very well. The presence of very large volcanoes at the surface indicates that Mars through time has been getting rid of heat. How warm is the interior of Mars? Is there seismic activity (Marsquakes)? Is there life on Mars today? The Mars Exploration Program currently has five operating missions at Mars to help address these questions. Additionally, other countries and space agencies have missions at Mars right now too! Future We are not done studying Mars. NASA will be launching the Insight mission in 2018 to study the interior of Mars. For the first time, we'll get sophisticated geophysical measurements from the interior, including heat flow and measurement of seismic activity. In 2020, NASA will also send the Mars 2020 rover to continue seeking the signs of life on Mars. Another aspect of the Mars 2020 rover mission will be to collect carefully documented rock and soil samples that we hope to return to Earth for study. Other countries (and even some private companies) have also become very interested in Mars and will be sending spacecraft there. In 2020 alone, five other spacecraft are currently scheduled to launch: the ExoMars rover(European Space Agency), the United Arab Emirates Hope Orbiter, a Japanese orbiter, a Chinese rover and a SpaceX Dragon capsule. NASA is also planning to send humans to Mars sometime in the future. Preparations are being made, primarily through our robotic exploration in collaboration with the Human Exploration and Operations Mission Directorate (HEOMD) and the Space Technology Mission Directorate (STMD). The Mars 2020 rover will help us understand the current weather, winds, radiation, and dust environment, and will demonstrate technologies that will help humans once there. Science Goals Goal 1: Determine if Mars Ever Supported Life. Goal 1 is predicated on the idea that Mars and Earth may have been relatively similar worlds during their early histories, and as life arose relatively early on the Earth, whether life ever arose on Mars is a key question. This Goal is further divided into two objectives: A) Determine if environments having high potential for prior habitability and preservation of biosignatures contain evidence of past life, and B) Determine if environments with high potential for current habitability and expression of biosignatures contain evidence of extant life. Goal 2: Understand the Processes and History of Climate on Mars, Goal 2 concerns fundamental questions about how the climate of Mars has evolved over time to reach the current state, the processes that have operated to produce this evolution, and whether the Martian atmosphere and climate reflect features that are universal to planetary atmospheres. This Goal is further divided into three objectives: A) Characterize the state of the present climate of Mars' atmosphere and surrounding plasma environment, and the underlying processes, under the current orbital configuration, B) Characterize the history of Mars’ climate in the recent past, and the underlying processes, under different orbital configurations, and C) Characterize Mars’ ancient climate and underlying processes. Goal 3: Understand the Origin and Evolution of Mars as a Geological System. Goal 3 seeks insight into the composition, structure, and history of Mars as a planet, through deeper understanding of its surface and interior. The investigaton of Mars is a compelling scientific exploration in its own right, but the planet also might once have hosted potentially habitable, Earthlike environments. This Goal is further divided into three objectives: A) Document the geologic record preserved in the crust and interpret the processes that have created that record, B) Determine the structure, composition, dynamics, and evolution of Mars’ interior and how it has evolved, and C) Determine the manifestations of Mars' evolution as recorded by its moons. Goal 4: Prepare for Human Exploration. Goal 4 encompasses how robotic flight missions can help prepare for potential crewed missions (or sets of missions) to the Mars system, and how these precursors can “buy down risk” that is inherent to any mission by acquiring precursor information that can be acted upon during design, implementation and operation of these future missions. This Goal is further divided into four objectives: A) Obtain knowledge of Mars sufficient to design and implement a human mission to Mars orbit with acceptable cost, risk, and performance, B) Obtain knowledge of Mars sufficient to design and implement a human mission to the Martian surface with acceptable cost, risk, and performance, C) Obtain knowledge of Mars sufficient to design and implement a human mission to the surface of either Phobos or Deimos with acceptable cost, risk, and performance, and D) Obtain knowledge of Mars sufficient to design and implement sustained human presence at the Martian surface with acceptable cost, risk, and performance. Gallery MarsPathfinderTwinPeaks.png Curiosity Mars Rover.jpg pia19839-galecrater-main.png Mars surface 3.jpg Mars surface 2.jpg Mars sun.jpg Category:Real Life Planets Category:Planets